Automatic carbonization of filaments



March 29, 1949. G. A. FREEMAN :fr A1. 2,455g54 AUTOMATIC CAHBONZATIN OF FILMENTS 5 Sheets-Sheet 1 Filed June 22, 1943 Ammann O MN u m uw mfumwmm 5MG Gf.. VDM

QLHHUH huw March 29, 1949. G. A. FREEMAN Erm. 2,455,854

AUTOMATIC CARBONIZATION 0F FILAMENTS Filed June 22, 1945 l 5 Sheets-Sheet 3 1553 5 @far/F752 x 19M/L /F/EE @y INVENTORS t. G. H. FEEMHN J6 J H. GEEF/v BYWMW ATTORNEY March 29, 1949. v G, A, FREEMAN ETAL 2,465,864

AUTOMATIC CARBONIZATION OF FILAMENTS Filed June 22, 1943 5 Sheets-Sheet 4 15.2 i 34 sa 309 5W zw f 5g, l 276 5J 259 I gg 155 j j conf-2:5555 qu? 134 297 INVENTORS X' 64 :192 61TH- FKEEMHN 4 J. ff GKEEA/ agg. BY

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:v i .ATTORNEY March 29,1949. G. A. FREEMAN ETAL 2,435,354-

AUTOMATIC CARBONIZATION OF FILAMENTS Filed June 22, .1943 ,5 sheets-sheet 5.

ATTORNEY Patented Mar. 2e, 1949 @Milian AUTOMATIC CARBONIZATION O5' FILAMENTS George A. Freeman, East Orange, and James H.

Green, West Orange, N. J., assignors tc Westinghouse Electric Corporation, East Pittsburgh, Pa., a corporation of Pennsylvania Application l-June 22, 1943, Serial No. 491,780 I (Cl. L18-13.1)

15 Claims. l

-means for automatically damping the current controller to prevent hunting when the moving pointer reaches an oscillator coil set at a desired point.

An added object of our invention is to provide means to delay the application of power, to the filament to be carbonized, while the treating bot'- tle is being purged.

A still further object cf our invention is to provide means to delay lowering of the iilamentcarrying mount for a short cooling period after carbonization to prevent oxidation of the parts.

An additional object of our invention is to provide means to disable the control buttons during carbonization, so that accidental lowering of the mount during such operation cannot happen. 1

y Another object of our invention is to prevent starting of the carbonization cycle with the wrong mount in position. 5

An additional object is to form uniformly I carbonized thoriated tungsten filaments.

^ cally shutting off said current when the voltage producing it reaches a predetermined value.

Other objects and advantages of the invention, relating to the particular arrangement and construction of the various parts, will become apparent as the description proceeds.

Referring to the drawing: Fig. 1 is a. front elevational view of apparatus embodying our invention. Y

. rying a iilament to be carbonlzed.

Fig. 3 is a schematic diagram showing the general principles of the invention in order to make it easier to understand the detailed description.

Fig. 4 is a diagrammatic showing of the arrangement which we prefer to use in the control ammeter.

Fig. 5 is a portion of the complete Wiring diagram of apparatus which We may use in the practice of our invention.

Fig. 6 is an adjoining portion of the wiring diagram of Fig. 5.

Fig. 7 is an adjoining portion of the Wiring diagram of Fig. 6.

Before describing the apparatus and opera tion thereof, it might be well to point out that We propose to accomplish 'carbonizatiom as for activation, by surrounding the filament with a reducing atmosphere, such as hydrogen, carbureted with benzol or other suitable hydrogen vapor, while heating said filament as by means of electric current maintained at a critical value. The degree of filament carbonization is accurately controlled by closely regulating the current until the filament resistance increases, due to its increasingcarbonization, to a predetermined point. As the current is held constant, the voltage cross the filament is proportional to its resistance. As soon as the resistance-determined' voltage rises to a predetermined value, thecurrent is automatically shut off.

The invention involves means to accomplish the above operations automatically, in order to obtain uniformity of the product, as well as speed of production. A simplified diagram, as well as the entire commercial apparatus, will be described. The latter may be separated into the following parts, in addition to the benzol vapor supply:

1. The mount raising and lowering mechanism.

2. The power supply.

3. The filament carbonizing circuits.

4. The control ammeter and voltmeter cir cuits.

5. The direct current supply.

-6. The stabilization of the filament carbonizing current. l

7. The termination of the current flow upon a predeterminedvrise in voltage, and

8. The time delay relays.

GENERAL DESCRIPTION The hydrogen picks up a reasonably constant percentage of hydrocarbon vapor, as by passing from ajet approximately one inch .above the level @www of the liquid benzol. Evaporation causes the liquid level to fall, but at a very slow rate in view of the reserve in the leveling tank.

The current regulator and voltage shut-off cir-v tor output to operate a relay to cut off the power when the voltage on the filament being carbonized reaches a predetermined value. The current controlling instrument, however, makes use of the continuous, but rapid, change in the oscillator output voltage as the instrument pointer vane moves within the oscillator coil. The current regulator output controls the amount of direct curv rent in a saturable reactor, Iand in this way exerts its eiect' upon the load current.

Due to inertia elects or" the current controlling instrument pointer, and the magnetic field of the saturable reactor, there is a tendency for violent hunting on oscillation of the current about the desired value. This is eliminated by the use of diierentiating circuits which damp the hunting oscillations. The damping is proportional to the speed of the pointer movement and, therefore, is proportional to the first derivative of the current. It exists only when the pointer is moving in the control range, and thus acts as a narrow "trap to hold the pointer at the desired spot on the scale. Any tendency for the pointer to go up is opposed by a voltage in the instru ment to push it back. As the pointer starts to drop it is opposed by a voltage opposite in polarity which holds it up. The position of the pointer is denitely fixed thereby and holds the load current likewise xed.

With the apparatus used, two means simultaneously act asproportional to the rst derivative One is a connected winding of' of the current. one of two turns around the D. C. winding of the saturable reactor and in series with the current instrument coil. The voltage induced in this extra winding is proportional to the rate of change of the magnetic ux through the D. C. leg of the saturable reactor, which is in turn proportional to the rate of change of the oscillator output voltage.

The other rst derivative voltage is obtained by starting with the oscillator output voltage itself and applying it through a xed condenser directly to the ammeter operating coil. The direct current voltage, of course, does not pass the condenser, but any variation in it changes the charge on the condenser, at -a rate proportional to the rate oi change of the D. C. voltage. The condenser charging current which is proportional to the rate oi change of the D. C. voltage is made to pass through the meter.

It is desirable to use together both methods of obtaining the first derivative control, since each ties back to one of the inertia components. Any

movement of the pointer results in a current pulseA operating coil of the am- 4 prevent acurrent surge immediately after power is turned on, it is desirable for the pointer to move up to the oscillator coil index pointer as quickly as possible. A stop below the index pointer, is provided for the moving pointer to keep K the distance of travel short. In the direct current power supply, a time delay circuit is provided to prevent a sudden change in the C bias and hence the saturation current. This gives the pointer time to move before the current rises too high.

Automatic control is effected by employing a number of relays which delay the turning on of the power while purging the treating bottle, de-v lay the lowering of the mount for a short cooling period after carbonization is complete, completely disable the central buttons during carbonization so that accidental lowering of the moun-tcannot occur during carbonization, and prevent the starting of the carbonization cycle with the wrong mount in position.

GENERAL DESCRIPTION or Prc. 1 AND THE CARBoNIzINo VAPOR SUPPLY Referring to the drawing in detail, and first considering the general view shown in Fig. l, we

have the carbonizing bottles II and I2, which may be constructed of any desired material such as steel, and alternately receive filament mounts I3 and I 4, one of which is shown in detail in Fig. 2. Each mount, for example, may comprise a iare tube I5 having a press I6 through which lead-in conductors I'l and I8 extend to a lament I9, the central portion of which is supported on an arbor 2i. The press and adjacent portion of the iiare are shown protected, as by a metal shield 22 which ts thereover. The flare tube I5 is, as usual provided with an exhaust tube 23, opening at its upper end therethrough and throug the protector, as indicated at 24.

Each treating bottle has la pipe connection 25 from a supply of carbureted gas, which in the 'present instance is intended to be hydrogen carrying benzol vapor. For this purpose hydrogen is admitted through the pipe 26 above the level of a supply of benzol 21, which may be viewed through the glass window 28 in the carbureter chamber 29. tially constant by having the chamber 29 communicating with a larger chamber 3D, as by means of pipes 3l and 32, so that the level drops very slowly. When considered desirable, the benzol is replenished by openingthe valve 33 and admitting more through the pipe 32 from the large supply tank 34. This carbureted gas supply apparatus is supported in -any desired manner, as by means of framework 35.

The treating bottles II and I2 and their connecting pipes are supported on a standard 35 having cross arms 3l and 38, which hold said bottles, as by encircling bands 39, 4I, 42 and 43. The standard 36 projects from a table or bench 44 having legs 45, and below` the top of which is disposed apparatus 46 for alternately raising and lowering the mount-supporting means 47 and 48 for the carbonizing cycles,

To the left of the carbonizing bottles, as viewed in Fig. 1, is mechanism 49 consisting of a control ammeter, oscillator and amplifier 5I, a control voltmeter, oscillator and ampliiier 52, and a series of indicator lamps, 'that is, a green lamp 53, a red lamp 54, and a yellow lamp 55,- to respectively show when the power is on, when the carbonizing cycle is on, and when the carbonized filament may be removed. Below the indicator lamps arethe main switch 5f., the starting'buttonril, the reset The level is maintained substanbutton sa, and the mount nfs lever 59.' Below these devices are the indicating ammeter 6|, the manual current regulator or transformer selector 62 (which simultaneously selects both primary and secondary coils, as shown in Fig. and the indicating voltmeter 63. The indicating instruments are used in addition to the control ammeter and voltmeter in order to obtain accurate readings when desired. l

DESCRIPTION or Sonst-uric DIAGRAM or FIG. 3, WITH Rari-.armor 'ro F1os. 1 AND 4 cuit breakers (not shown), power line 64, primary winding 65 of filament transformer 66, and then alternating current coils 61 and 68, of what we choose to call a "saturable reactor '10, which is really a reactance device adapted to be automatically varied in value for the purpose of controlling the current through the filament being carbonized. From the coil 68 current passes back to the main switch along power line 69 through normally closed contacter or switch 1I, adapted to open upon release of normally energized relay coil |23 by action of any suitable means, such as return spring 40.

The power supply for carbonizing the iilament is from the secondary Winding 'I2 of the transformer 66, and the current therefrom is controlled by passing through line 'I3 to the primary windlng 'I4 of a control or current transformer '15, and from thence back. through line 'I6 to the filament. Current from the secondary winding of the transformer 'I5 goes through the indicating ammeter 6I to a copper oxide rectifying network "I8, from which rectiiied current emerges to pass to the actuating coil 'I9 of the control ammeter 5|, through lines 8| and 82, in series with a direct current coil 83 of few turns on the saturable reactor through lines 84- and 85. Resistances 20, B9, 90, |00 are used to load the circuit and adjust the range of the instrument;

The ammeter indicating needle or pointer 86 carries a vane or ag 8l, which is normally external to (or below, nsofaras scale reading is concerned) the eld of the control coils 88 and 89 of an oscillator triode circuit (shown in detail in Fig, 7) for controlling the iiow of carbonizing current and preventing hunting of the ammeter needle 86. The coils 88 and 8S are carried by and movable with a setting hand or pointer 50, which also carries a stop lll to limit return movement of the pointer 86 (see Figs. 1 and 4). The output of the oscillator is amplied and fed back through lines 9| and 92 to rectifier and amplifier S3, the D. C. output from which is fed back to direct current coil 94 on reactor 'IU through lines 95 and S6. Power for the rectifier andamplifier 93 is received from the power lines through lines 91 and 98, and for the ammeter, oscillator and'amplilier 5| through lines 99 and |0I.

It will readily be seen that we have two means vwhich act simultaneously and proportionately to the speed of movement of the ammeter pointer 86 to stabilize the carbonizing current One is thc D. C. coil 83 on the reactor i6, which is directly connected in the actuating circuit of the ammeter through lines 'Sli and 85. The other is by the oscillator output feed-back voltage, which is applied through differentiating condenser |02, and leads |03 and |04, to the actuating coil 79.

The direct current component of the feed-back through lines 9| and 92, of course, does not pass the condenser, but variations in it causes a condenser charging current which is proportional to the rate of variation, thereby serving as an additional stabilizer.

Nuvi

The control voltmeter, oscillator and amplifier 52 is supplied with power through lines |01 and |08', and is generally similar to the ammeter, oscillator and amplifier 5I in construction, except as will now be explained. The Voltmeter actuating coil I 09 is connected across the carbonizing current line through lines and l2, rectifying network |I3, lines H4 and'l |5. Resistances 2B', SD', |00 serve to load the circuit and adjust the range of the instrument. The voltmeter needle or pointer H6, like that of the ammeter, carries a vane or flag II'I which is normally external to (or below, insofar as scale reading is concerned) the iield of the control coils ||8 and IISl of an oscillator triade circuit (shown in detail in Fig. '7) for finally shutting off the ow of carbonizing current when the voltage necessary to cause said current increases beyond a predetermined Value. The output of the oscillator is amplified to operate a small relay |23 through lines |2I and |22. Whenthe voltage of the carbonizing circuit rises suiiiciently, said relay |23 is substantially de-energized and releases the contactor or switch '|I, allowing it to open and de-energize the carbonizing circuit through the lament I9, -ending the carbonizing cycle.

OPERATION 1N ACCORDANCE WITH SCHEMATIC DIA- GRAM or' FIG. 3, AND WITH REFERENCE ro F1os. 1 AND 4 In 'brief the operation of the apparatus previously described is as follows:

Upon setting the selector handle 62 (see Fig. 1) in accordance with the iilament to be carbonized, and the ammeter and voltmeter setting hands 5U and 60 at the desired control points on the respective scales, operating the mount lift switch or lever 59 to place the desired iilarnent in position for carbonizing, and closing the main switch 56, visually indicated by energization of a green light designated 53, the power lines become energized, after which the carbonizing cycle may a relay closes the circuit to start the energization and carbonization of the positioned filament I9.

The energization of the carbonizing circuit also energizes the voltmeter and ammeter control circuits, the feed-back circuits between amnieter coil 79 and the reactor 70 effectively smoothing out and stabilizing the current throughsaicl lament |9 by controlling the residual voltage applied to the primary winding 65 of the lament transformer 66. The carbonizing circuit through the filament I9 is maintained until the voltage, s

as measured by the output circuit from the voltmeter oscillator, reaches a suiicient value to air from below it through pipe line |41.

' suiciently. At the end of this timing cycle, the

yellow lamp 55 (seeFig. 1) is energized. After the filament has been withdrawn from the treating bottle conditions are restored to initial position for the beginning of a new carbonizing cycle.

the degree of carbonlza- DETAILED DESCRIPTION WITH REFERENCE r FIGS. 1, 4, 5, 6 AND '1 1. The mount raising and lowering mechanism The mount raising and lowering mechanism 46, shown generally in Fig. 1, is also represented diagrammatically in Fig. 6. In said latter iigure, is shown at the left an air cylinder |24 in which reciprocates a piston |25, the rod |25 of which has mount-supporting means 41 (see Fig. 1) and an adjustable switch-operating arm |21 adapted to open and close an associated single-acting switch |28 as the rod moves one Way or the other. The mount-actuating mechanism is approximately duplicated on the right, as indicated by the cylinder |29, piston |3|, rod |32, mount-supporting means 48 (see Fig. 1), switch actuating arm |33 and double-acting switch |34. `Both cylinders are connected to a compressed air supply line |35. through control valve |36, the handle |31 of which terminates in prongs |38, between which a projection |39 on an armature |4|, reciprocable between solenoids |42 and |43, is provided.

These solenoids are alternatively energized by the mount-lift switch 59, which in the position shown in full lines has taken power from line 64,' through line |44, normally closed relay-controlled switch |45, line |46, left element of mountlift switch 59, left solenoid |42, right element of mount-lift switch 59, and on through line |40 to power line 69. This, as illustrated, has drawn the armature |4| into the solenoid |42 and admitted compressed air through line |48 below the piston |25 to push it to the upper end of the cylinder |24 while exhausting air' from above said piston through line |41. This raises the mount supporting means 41 and its mount i3 into the carbon-zing bottle while at the same time lowering the mount |4 from its carbonizing bottle |2, releasing the switch |28 to allow it to open, and moving the switch |34 from engagement with its upper contact to engagement with'its lower contact.

This latter operation is performed by means of the member |33 on the piston rod |32, by admitting compressed air against the upper end of the piston |3|`th`rough line |48 and exhausting This raising and lowering operation may be repeated after each mount-carried filament has been car-A bonizecl and replaced by another one, so that first a filament at the left and then one at the right is carbonized, and so on alternately.

2. The power supply The power supply in the present instance, as represented in the embodiment of our invention of Figs. 5, 6 and 7, involves the use of 226 volt lines '64 and S3. Power passes from power line *64 through lines 15| and |52, to energize the green lamp 53 through resistance |53, and line |54 to power line 69. as an indication thatthe power is on, as shown in Fig. 6.

The current and voltage control apparatus of Fig. 7 receive power, for the primary coils |55, |56, |51 and |58 of their transformers |59 and |66, from the power line 54 through line 99, coils |55 and |56, and line |68 to power line 69; and from the power line 64 through lines 99 and |01, coils |51 and |58, and line |68 to power line 69.

The primary coils of the rectifier and amplier transformers |6|, |52 and |63, shown in Fig. 5, receive power from the line 64 through line |64, which from there passes in parallel through primary coils |65, |66 and |61 and line 98 to line 59.

The power of the primary winding 65 of the filament transformer 66, shown in Fig.' 5, is drawn from the power line 64 through normally-open relay-controlled switch |69, also passing through the coils 61 and 68 of the saturable reactor 10 and line |1|, on to the power line 69 through normally-open relay-controlled switch |12.

3. The flament-carbonzzing circuits The preferably thoriated tungsten filaments I9 to be carbonized receive their electric current from the secondary winding 12 of the transformer |56. When said filaments are in the positions illustrated in Fig. 5, the switch |28 (see Fig. 6) is open so that no power is received by the relay |13 and the relay-controlled switch |14 remains in engagement with its lower contact, thereby allowing current to pass from the secondary coil 12 (on closure of the switch |69 upon energization of the relay |15) through line 13, selector switch 62, primary coil 14 of selected instrument transformer 15, through switch |16 (or adjustable testing resistance |11 when the switch is thrown to other position), relay-controlled switch |14, line |80, left hand lament I9, and back to the 'secondary coil 12 through lines |18 and 1S.

When the mount lift switch 59 is moved to thel 'position shown in dotted lines in Fig. 6, the left hand filament I9 is withdrawn from the bottle and the right hand filament |9 moved up into the bottle |2. This causes the arm |21 to cose the .switch |28 and current to pass from power |9, as viewed in Fig. 5. The energization circuit is generally the same, except that the power does not pass through line |80, but instead passes from switch |14 to line |81, through right hand larnent |9, then through lines |88, |89, and 15, back to the secondary winding 1.2.

4. The control ammeter and 'voltmeter circuits The control of the carbonizing current is by a circuit builtaround the dual triode vtube |96, type 53 (see Fig. '1)."This is an indirect-heater type of tube. The left hand triode section, is used as a high frequency oscillator with a selftuned grid tank circuit. Alternating current is supplied from the transformer |59 to the tube |66. Rectifled plate current goes through a load 86, switch 58, and line |49 to resistor |97, the drop across which is used to bias the grid |98 of the right-hand or amplifier section of the tube |96.

The amplified output connects through lines 9| and 92 to the rectifier and amplifier 93 (see Fig. from which a. rectied output circuit passes through line 95 to coil 94 of reactor 79, and back through line 93 to rectifier and amplier 93. The variation; inthe current passing through the coil 9d, through this connection, control the current through the filament being carbonized by affecting tre magnetization of the core of reactor 70.

Reverting now to thel details of the ammcter control instrument circut 5| (see Fig. '7) we find that the oscillator grid l99 is connected through line 20| and condenser 292 to coil 88, from whence the circuit passes through it and on through coilA 89, resistance 203, and back through line 206, air condenser 205, and adjurable inductance 20B, to plate 207 of said oscillator section. Energy is supplied to the plate circuit by means of secondary winding 208 of transformer |59. This energy is alternating current and the plate element 207, in conjunction with its vcathode 209, acts as a self-tuned oscillator.

The plate circuit of the amplifier or right hand section of the tube |96 is energized from-secondary winding 2|| of the transformer |59, so that it also acts as a self-rectified triode. across this amplifieris used, in turn, to bias the grid |99 of the oscillator section through re* sistances |95 and 2|2. A condenser 2|3 is placed across the output lines |03 and |04', from the grounded winding 2|4 to the winding 2H, to smooth out the energy peaks of the amplied plate current during the negative portion of the rectified cycle. Secondary windingf 2M is used as additional bias to fix the plate energy levels upon proper operating points of the triode graph. The winding 2|5, of course, supplies the power lto heat the cathodes 299 and 2|G of the tube |90.

A leak resistance 200 is provided between thev coils 79 and 89 to dissipate static electricity.

By virtue of this circuit arrangement, the 0scillator triode section normally operates at full radio-frequency excitation, with the plate current normally low. The drop across the bias re sistor |97, in parallel with condenser 2|7, is low so that grid bias on the triode amplifier section' comes detuned, with a consequent rise in the plate current of the oscillator, or left hand, section of the tube |95. The bias across the re- The drop' 87 is outside of the coils 88 and 89, and cut-off, when the flag 87 is between said coils. These sharp swings are important, as upon the flag 87 leaving the control coils 88 and 89 reverse action takes place and the amplier plate current sharply rises. The plate current swings as a result of the pointer passing through the coils 8 8 and.99'are, therefore, sharp, abrupt and rapid, resulting, through the action of the circuit through the differentiating condenser |02, in a strong control on the movement of pointer 8B and a corresponding control of the current through the filament being carbonized.

The constants of ammeter and oscillator circuits 5| are preferably so chosen that the amplier plate current swing through the relay |23 from nag positions entirely out of the coils, to iiag position one-quarter within the coils is between about 20 milliamperes and 2 milliamperes.

"This current swing may be made any value up to the saturation limit of the amplifier triode section. Saturation value of the zero grid bias point in said section is approximately 40 millisstor |97 therefore rises, increasing the negative bias on the grid |98 of the right hand or amplier section, thereby lowering the control plate current. As this plate current drops, the consequent voltage, which is used to bias the grid |99 of the oscillator section, decreases. This reduces the negative bias of said grid |99 which, 7 y in turn. due to increase of the plate current of the oscillator', increases the bias across resistance |97. further increasing the negative bias of the section grid. The net result of this ent to approximately the cut-oli pint of the cniplieisection of tube.

The plate current of the amplier section will therefore alternate between a high value, as fixed by the components in the 4circuit when the flag action to produce n sharp drop in theA |62. Increased plate current increases the mag- I -netization of the core ofthe reactor which amperes. Since the maximum plate current drawn at any time is 18 millimeters and the filament is operated at of its regular voltage, the tube |99 has a long life expectancy. The

output from the amplifier section of the tube |96 passes from the plate |70 out through coil 2|| and lines |04 and 9|, and back through lines 92.

and |03, to and from the bias-supply and input connections, respectively, of the rectiiier and amplifier 93.

' 5. The direct current supply A push button 2| 8 (see Fig. 5) is provided to short the bias voltage provided by the dual recti- Iier tube 229, supplied with plate current by the secondary coils 23| and 232, and with cathode heating power by the coil 232, of transformer i |63, and smoothed out by condenser 233. The

voltage-divider resistance 2|9 is for the variable' and lines 224 and 225. `When in operation the switch 223 is raised, by energization of the relay |75, the charge in the condenser 22| tends to hold conditions normal, but discharge thereof gradually lowers the bias and plate current starts from the connected amplifier and 'rectifier tubes 227 and 22S supplied with power by the secondary coils 234 and 235 of the transformer |6| and allows more current to flow through the filament being carbonized. When the pointer 99 (see Fig.

7) of the control ammeter 5| reaches the con? cillator output voltage change which is reflected` in the D. C. supply to the saturable reactor. By the connection through line 92 (lilig. 5l to the grids 236 and 23T Of the tubes 227 and 228, ampli l accessi.

6. The stabilization of the filament carbom'ziny current Two circuits are used for stabilizing the niament carbonizing current. One is a direct conl nection from the operating coil 19 of the ammeter (Fig` 7) through lines 82 and 84 to coil 83 (one or two turns around the D. C. coil 94) of the reactor 16 (Fig. 5) and the line 65 in series with the supply from the copper oxide rectifier network 18 (Fig. '7) and back to the coil 19. The actuating current to the coil 19 is from the secondary coil 11 (Fig. 5) (selected by the switch 62) of the transformer 15, through ammeter 6|, lines |9|, |92 and |93 (Fig. 7), rectifier-network 18, on through the circuit just traced through the coil 83, to the coil 19, and back through line 8|, rectifier network 18, lines |95 and |96, and

through switch 62 (Fig. 5) back to coil T1.

It will thus be seen that any variation in the D. C. current which passes through the coil 94 will have a corresponding eiect on the induced voltage in coil 83 of the saturable reactor 16. In other words, the voltage induced in the extra winding 83 is proportional to the rate of change of the magnetic iiux in the direct magnetic circuit of the reactor 16, which is in turn proportional to the rate of change of the output from the rectier 93 and so serves to feed back a damping or stabilizing current to the coil 19.

The other stabilizing circuit is from the tube |96 (Fig. '7) output line |63 through resistance |05 and differentiating condenser |02 to the actuating coil 19 of ammeter 5|. The other side of the coil 19 is connected to the other output line |04 through line 82 and resistance |06.

1. The termination of current flow upon a predetermined rz'se in voltage 1 The control of the length of time the carbonizing current flows is by a circuit built around the dual triode tube 23B. This is similar to the tube |96. The lett hand section, as viewed in Fig. 7, is used as a high frequency oscillator with self-tuned grid tank circuit consisting of an air condenser 239 and appropriate adjustable' inductance 24|. Alternating current is supplied from the transformer |66 to the tube 238. Rectliied plate current goes through a load resistor 242, the drop across which is used to bias the grid 243 of the right hand or ampliiier section of the tube 238. A condenser 263 is in parallel with this resistor.

The amplier output lines 2| and |22 of the tube 238 are connected to the normally energized relay |23`in order to open the switch 1| to de-energze relay (Fig. 5) and terminate the flow o carbonizing current when the voltage of the filament being carbonized has reached a predetermined point. De-energization of the relay |23 also allows the switch 244 to close, energizing the indicator 245 connected between lines 64 and 69 in series with condenser 246 t'o show that the carbonizing cycle has been completed.

Reyerting now to the details of the network.4

-bonizing cycle disposed below the coils -of the coil of relay |23 and resistance 251.

the relay |23 normally receives enough current to hold the switch 1| against its lower contact and the switch 244 open. This of course means that the iiag ||1 is at the beginning of the caf- 8 and H8.

When the voltage rises to the predetermined point, this flag passes between the coils H8 and ||9, detuning the oscillator circuit, thereby effecting an increase in the oscillator plate current and a corresponding large decrease in the amplifier plate current, that is, sufficient to de-ener-v gize the relay |28 and allow the switch 1| t0 open and terminate the flow of carbonizing current. Opening of the switch 1| causes an engagement thereof with the upper contact 284, thereby energizing the relay 265' (Fig. 6) to operate the timing clock 28| to start timing of the cooling period.

Showing the similarity of the voltrneter control circuit with the ammeter control circuit, it

is pointed out that the oscillator grid 241 is connected through line 248 and condenser 249 to coil ||8, from whence it passes through it and on through coil H3, resistance 25|, and back through line 252, condenser 233 and variable inductance coil 24|, to plate 253 of said oscillator section. Energy is supplied to the plate circuit by means of secondary winding 254 of transformer |66. This energy is alternating current and the plate element 253, in conjunction with its cathode 255, acts as a self-tuned oscillator.

The rectied plate current therefore goes through load resistor 242, the drop across which acts as a bias for the grid 243 of the right hand or' amplifier section of the tube 238.

The plate circuit of the amplifier, or right hand section of the tube 238, is energized from secondary winding 258 of the transformer |66, so that it also acts as a self-rectiiied triode. kThe drop across this ampliler is used, in turn, to biasthe grid 241 of the oscillator section through part A condenser 258 is placed across the output lines 2| and |22 to smooth out energy peaks during the negative portion of the rectified cycle.

Secondary winding 259 is used as additional bias to fix the plate energy levels upon proper operating points of the triode graph. The winding 26|, of course, supplies the power to heat the cathodes 255 and 262 of the tube 238. As in the ammeter control circuit, a leak resistance 266 is provided between the coils |09 and H9.

8. The time delay relays In order to prevent energization lof the lament for carbonizing purposes prior to complete ushingv of the treating bottle, Il or |2 as the case may be, and an explosion of a mixture of carbureted hydrogen withair, a timing device 261 vis provided with a relay 268 (see Fig. 6) which, upon energization, closes switches 269 and 21| against upper contacts 212 and 213, thereby starting operation of a clock or timing element 214. After thelapse of a. time for which the clock has been set, downward movement of its arm 286 opens the switch 269, by withdrawing it from its contact 212', and pulls the switch 21| from engagement vwith upper contact 212 into aeaaeefi the carbonization current has been cut ofi, closes switches 216 and 211 against upper contacts 218 and 219, thereby starting operation of the clock or timing element 28| until a length of time, of say ten or fifteen seconds in accordance with a predetermined setting, has elapsed. The switch 216 is then opened, and the switch 211 pulled down from engagement with its upper contact 219, into engagement with lower contact 282, by downward movement of the clocks arm 29|), to thereby energize yellow signal lamp 55 to show the operator that the carbonizing cycle is complete, including the cooling period, and that the lament can be removed from the bottle and its support, by actuating the mount lift switch 59, which automatically removes the carbonized filament and, at the same time, feeds a new unearbonized filament into the other treating bottle.

The timing clocks are automatically reset as power to the timers is interrupted. This releases the electrical interlock formed by one contact in the relay part oi timer.

in Figs. 5, 6 and 7 v Prior to the actual carbonization of 'a mounted larnent the apparatus is adjusted and tested for the type of filament to be carbonized, Foi` this purpose the switch 62 (see Fig. 5) is set on the proper contact to select the proper transformer, in this case 15, to agree lwith the scale of the indicating ammeter 6|. The resistor |11 is set to a figure agreeing with that of the lament to be carbonized, and switch |16 moved to its left hand contact |99, thereby shorting the connection to the filament |9 and placing the adjusted resistor |11 in the circuit usually employed for carbonlzation.

After closing the main switch 56, which energizes the green lamp 53 (see Fig. 6), the push button 51 is depressed, closing the circuit through the relay coil 268 of timer 261, initiating the ush-tinecycle, and energizing the red lampv 54. Of course, in the testing, the flush-time cycle has no function, but in order to determine that it is operating satisfactorily, the timing thereof should be noted. This establishes a holding circuit by the operation of the relay 292, after a time-lag, and the mount-lifting circuit is de-energized, unnecessarily in the present instance because there is no actual carbonizing of a lament.

When the timer 261 finishes, it starts current through the testing resistor |11 (Fig. 5) and the indicating ammeter 6|, indicating voltmeter 63, control ammeter and associated circuits 5| and control voltmeter and associated circuits 52. The controlling ammeter 5| is then set to give the desired current-for carbonizing, as indicated on the ammeter 6|, and the adjustable resistor |11 is set to give the desired voltage reading on the indicating voltmeter 63.

the voltage increases to the desired extent, as at the end ofthe carbonizing period.

After complete setting and testing a mount for carbonization is placed. say on the left mount support member 41 and the mount lift switch 59 operated to cause it to be moved into the treat ing bottle |l, as illustrated in Fig. l. drogen supply is admitted to the pipe 26 so that lt starts flowing into the carbureting chamber 29 and out of the pipe 25 into the treating bottles il and I2. The main switch 55 is closed energizing the green lamp53, and the push button 51 Voltmeter 52 is then adjusted so that the power circuit opens 'when depressed, which energizes vthe red lamp 54 to indicate the beginning of a. cycle, and causes a ow of current from the power line 64 through lines 283, 284 (Fig. 6), relay 268, lines 285, 286, normally closed switch 281, push button 51, normally closed switch 288, line 289, switch |34, depressed when the left hand mold holding member is up, as assumed, line 29|, resetting button 58, and line |40 to power line G9.

In order to avoid .the necessity of holding the push button depressed for any long period of time, second timer means is provided establishing a holding circuit through lines 296 by operation through resistance 293 of the relay 292, after a time interval predetermined by time delay member 294, closing the switch 295. course means that the timing period for hushing the bottle prior to the initiation of the carbonizing treatment, has been initiated. The operation of the relay 292 also de-energizes the circuit through the solenoid |42 by opening the switch |45, thereby making it impossible to withdraw the left mount-supported filament i9 from the treating bottle while the carbonizing cycle is in progress.

After the termination of the flushing time, as

indicated by the clock 214 opening the switch power line 69, to close the switch |69 and start the flow of carbonizing current through the lament |9. The lowering of switch 21! of timer 261 (see Fig. 6) from engagement with its con tact 213 breaks the power circuit through line 219 to, and stops the clock 214.

The energcation of the carbonizing circuit also energizes the circuits of the indicating ammeter 6| and voltmeter 63 (Fig. 5), the control ammeter apparatus 5| and the control voltmeter apparatus 52 (Fig. 7). The feed-back circuit between the amplier side of the tube |98 through'lines Sl and 92 and reactor coil 94, as y wellas the direct connection between the ammeter coil 19 and the coil 83, assist one another in smoothing out and stabilizing the current through the filament being carbonized, as will be understood.

The carbonizing circuit through the filament I9 is maintained until the voltage on the filament |9- in the output circuit from the voltmeter control apparatus 52 is suhcient to cause the normal flow of current through the relay |23 .to substantially terminate to allow the switch 1| -to open, and thereby de-energize the relay |15 (Fig. 5) to allow the switches |69 Iand |12 to open and cle-energize the lamenttransformer 66.

De-energization of the relay |29'also allows the switch 1| to engage its upper contactA 264, which starts the timer 265 and prevents withdrawal of the lament until it has cooled for a predetermined period.v The operating circuit is from power lines 64, through lines 283 and 361, relay 285, lines 308, 309, 3|0, 3H, contact 254, switch 1|, lines 362 and 385, switch |34, line 2.9!, button 58, and line Hitl to power line 69. Closing of the Aswitch 244 shows completion of the carbonizing cycle by energizing the indicator 25.5. At the end of the predetermined cooling time the switch 211 is moved to engage its lower contact 282, energizlng the yellow lamp 55 snowing `the end of the This of i., .il/f 8. The current controlling ammeter is set so 55 that current, equivalent to the desired carbonizcycle. The engagement of the switch 211 with its lower contact 282 also energizes the relay 30B to open switch 288 and return the circuit to initial position. The apparatus is then ready for movement of the-mount lift switch 59 to its other position,v after the application of a mount-carried lament i8 to the mount supporting device 48, to lower the left hand filament and raise the right hand filament, prior .to beginning a new carbonizing cycle, this time in the treating bottle l2 instead of the bottle i l.

In brief, the operation of the apparatus will therefore be seen to be as follows:

1. Hydrogen supply turned on.

2. Main switch closed, energizing green lamp.

3. Set the switch 176 to engage its contact |90, reference being had to Fig. 5, so that testing resistor is in the power circuit from the transformer secondary '12.

4. The push button 5'? is depressed for a testing of the operation of the relay coil 258 of timer 2-61, as initiating a iiush time cycle, with energization of the red lamp 54.

5. A holding 'circuit should be establishedv by the operation of relay 292, after a desired time lag, and the mount-lifting solenoid circuit should be de-energized, making it impossible to secure any movement if the switch 5S is operated.

6. When the timer 251 finishes its operation, current should ilow through the testing resistor l '17.A

7. The energization of the testing circuit also .j

/fjenergizes the indicating ammeter and voltmeterfl and the control ammeter and voltmeter.

ing current, is indicated.

9. The resistor I 'l1 should .be set to give the de sire-d voltage.

10. The controlling voltmeter should be set so that the power circuit opens at the desired voltage, as when the resistor i'l'i is adjusted upwardly until the power is automzdically shut oir.

l1. The timer 266 then starts automatically to prevent the operation of the mount lifter apparatus for a predetermined period.

12. At the end of 'said predetermined period the timer 206 energizes relay coil B, which breaks rthe circuit to restore conditions to initial position and causes the yellow lamp to glow. Switch Il E put in full position.

13. Mount placed. (This will take place during `carbonizing cycle of previous lamp after starting machine.) 'L

14. Mount lift switch operated, dia-energizing relay coil 306 and yellow lamp 55. K

15. Push button 51 depressed, closing thecircuit through the relay coil 268 of timer 281, initiating flush-time cycle and energizing-red lamp 54.

16. A holding circuit is established by the operation of relay 292, after a ltime lag, and the mount-lifting solenoid circuit is de-energized.

17. When timer 261 finishes, it closes circuit to .energize filament for carbonizing.

18. The initiation of the carbonizing lcircuit also causes current to flow to indicating ammeter and voltmeter, and closing of the control ammeter and voltmeter circuits.

19. During carboniaation, the current through the filament is maintained constant. 'i

20. The carbonizing circuit is maintained until the voltage thereof rises to a predetermined `point, when it is broken by the control voltmeter. 75

21. Timer 26 is then started to prevent withdrawal of the lament until cooled sumciently.

22. At the end of the predetermined period, timer 256 energizes relay coil 306 which breaks circuit to restore conditions to initial position, and causes the yellow lamp 55 to glow.

23. The operator then begins again with step No. 14 and repeats.

24. If, during the operation of the apparatus..

it is desired to reset the parts to initial position, the push button 58 is depressed to break the circuit to the power lines.

From the foregoing disclosure it will be seen that we have pro /ided a method and apparatus whereby filaments which may be used for radio tubes or any desin d purpose are, after mounting, positioned in a treating bottle and automatically carbonized to a desired extent, safeguards being provided for preventing the application of'carbonizing current prior to complete flushing of the treating bottle and withdrawing the car-bonized filament until it and parts of its mount have cooled sufficiently to avoid undesired oxidation. Although We have shown a special form of mount and filament, it will be understood that We are not limited to this showing, as brdcagef and all other forms of iilaments, mounted or unmounted, may be treated. v

It will also be understood that the main purpose of showing Fig. 3 is to enable the reader' to more clearly understand' Figs. 5,v 6 and 7. The saturable reactor, illustrated diagrammatically in Fig. 5, is like that shown in Fig. 3 in that the direct current coils 83 and 93 are on the center or directly-magnetized leg of the saturable reactor core, as, distinguished from the end or alternating current legs of said core.

Although a preferred embodiment of our invention has been disclosed, it will be understood that modifications may be made within the spirit and scope of the appended claims.

We claim:

' 1. The method of carbonizing a, filament comprising heating to a carbonizing temperature by `passing a uniformly maintainedgurrentwthrough tn'acarbtd"e`d'ciffg"atnosphere Euntil its resistance, as indicated ,by.a.p`l'edete1`mined riSe in the yoltage of said current, reaches a predeterminedwalufa'd'then terminating the flow of said current.

2. The method of carbonizing a filament comprising introducing a mount holding such a lament into a treating bottle, supplying a carbureted reducing gas to said bottle, passing a. uniformly-maintained current throughsaid filament to heat it to a carbonizing temperature, and stopping the flow of said current when the voltageY .a treating bottle containing carbureted gas, passing uniformly maintained carbonizing current through the filament and thereby heating it to a carbonizing temperature only until the voltage thereof rises to'a predetermined value, holding the carbonized filament in position after termination of the carbonizing current until it has cooled to a predetermined extent, and finally withdrawing said carbonized filament from the treating bottle. ,I

5. Apparatus for carbonizing a filament comprising a compartment, means for introducing carbureted reducing gas thereinto, means for holding said filament-therein and surrounded by said gas, means for supplying stabilized car' bonizing current to said filament, and means for automatically terminatir g the flow of said current after the voltage necessary to cause the same rises above a predetermined value.

6. Apparatus for carhc nlzing a filament comi prising a. compartment, means for introducing carbureted reducing ges vthereinto, means for holding a filament therein While surrounded by said gas, means for maintaining a uniform carbonizing current through said filament, and means for automatically' terminating the 110W of said current when the voltage producing the carx bonizing current through said filament reaches a predetermined value. c

7. Apparatus for carbonizing a iilament comprising a treating bottle, means for introducing carbureted reducing gas thereinto, means forA holding said filament therein and surrounded by said gas, and means for supplying a uniformlymaintained carbonizing current to said iilament, after a predetermined delay allowing for ushing of said bottle, and means for automatically terminating the flow of said current after the voltage necessary to cause the same rises above a predetermined value. v

-8. Apparatus for carbonizing a filament when held on a mount comprising a treating bottle,

withdrawal of a mount until carbonization is complete, a timingdevice' for closing the carbonizing circuit to the iilament when a predetermined time after pushing the button has elapsed, an ammeter in the carbonizing circuit for closely controlling the strength of thecarbonizing current, a control voltmeter for shutting ofi the current through the filament when the voltage of said current reaches to a predetermined value, and a timing device in the circuit to prevent Withdrawal of the lament after termination of the carbonizing current until a suilicient coolingk period has transpired.

ll. Apparatus for carbonizing a filament when on a mount comprising a plurality of treating bottles, means for introducing carbonizing atmosphere Athereinto, means for holding a pair of mounts and operating them so that when one is moved into one treating bottle the other is withdrawn from the other treating bottle, a switch for controlling circuits for causing such Amount movement, a push button for initiating a cycle during which the treating bottles are lled with carbonizing gas prior to the application of carbonizing current to a filament, a timer for controlling the length of said cycle, means for establishing a holding circuit around the push button and effecting de-energization of the mount-lifting circuit to avoid withdrawal of a mount until carbonization is complete, a timing device for closing the carbonizing circuit to the filament when a predetermined time after pushmeans for introducing a carbonizing atmosphere thereinto, means for holding said mount in said bottle and surrounded by said atmosphere, means for passing substantially constant carbonizing current, closely controlled as to strength, through said filament, means for automatically stopping the flow of said current when the voltage causing it rises to a predetermined value, and means making it impossible to remove said iilament from said bottle until after a predetermined cooling I period.

9. Apparatus for carbonizing a filament when held on a mount comprising a treating bottle,

means for introducing a carbonizing atmosphere thereinto, means for holding said mount in said bottle and surrounded by said atmosphere, means for passing uniformiy maintained current through said filament to heat it to a carbonizing temperature, means for automatically stopping the flow of said current when the voltage causing it rises to a predetermined value, and means making it impossible to remove said filament from said bottle until after a predetermined cooling period.

10. Apparatus for carbonizing a filament when on a mount comprising a treating bottle, means for introducing carbonizing atmosphere thereinto, means for holding a mount and. operating it so that it may be moved into said treating bottle or withdrawn, fa switch for controlling circuits for causing such mount movement, a

push button for initiating a cycle duringe'hich the treating bottle is filled with Carbonia-ing gas ing the button has elapsed, an ammeter in the carbonizing circuit for maintaining the carbonizing current substantially constant during filament treatment, a control voltmeter for shutting oii the current through the filament when the voltage of said current reaches toa predetermined value, a timing device in the circuit to prevent withdrawal of the filament after termination of the carbonizing current until a suiiicient cooling period has transpired, and signal means for showing when the cooling period has elapsed and the filament may be Withdrawn upon the termination of the set cooling period.

12. Apparatus for carbonizing a iilament when on a mount comprising a plurality of treating bottles, means for introducing a carbonizing atmosphere thereinto, a pair of mount-holding devices, means ior operating them so that when one is moved into one treating bottle the other is withdrawn from the other treating bottle, means for closing a carbonizing circuit through the filament so held in a treating bottle, and means for preventing the application of carbonizing current to a filament when held on the device not in said bottle.

13. Apparatus for carbonizing a filament, comprising a 'lift device for holding a mount carrying said filament, a switch and associated apparatus for causing said device to lift said mount, a treating bottle into which said mount is lifted by said device, means for supplying said bottle.

with carbureted gas, a timing device having' a relay coil to initiate a flush-time circuit and energize an indicator lamp. means to establish a holding circuit by the `operation of a relay after a time lag, means to deenergze the mount lifting circuit, means to close a circuit to pass a carbonizing current through the filament, means to establish corresponding circuits to a control ammeter and a control voltrneter in order to maintain the current through said filament constant during carbonization, until the voltage thereof lrises to a predetermined va'fue ano the current ing a chamber containing a vaporizable liquid hydrocarbon for carbureting gas, an auxiliary chamber of relatively large volume connected to said chamber, whereby the level of the liquid in the latter remains substantially constant, means for introducing gas into said carbureting chamber and causing it to pass therefrom after carburetion into said compartment, means for holding a lament in said compartment and sur yrounded by said carbureted gasymeans for maintaining a substantially uniform carbonizing cur rent through said iiiament, and means for automatically terminating the flow of said current when the voltage of said current reaches a predeterminedvaiue. A

15. Apparatus for carbonizing a filament comprising a treating bottle, means for introducing a carbureted reducing gas thereinto, electrical means for moving said. lament into or out of said bottle, a switch for controlling circuits ior causing such movement, a push button for initiating a cycle. during which said treating bottle is filled with said gas prior. to the application of carbonizing current to a filament, a timer for controlling the length of said cycle. and second timer means for estabiishingaholding circuit around the push button and eiecting cle-energization of the filament-moving means to avoid filament withdrawal until carbonization is complete.

GEORGE A. FREEMAN. JAMES H. GREEN.

REFERENCES CITED The following references are of record in the nie of this patent: f

UNITED STATES PATENTS Number Name Date '390,310 Packard Oct. 2, 1888 1,367,124 Colby Feb. 1, 1921 1,529,597 Langmuir Mai'. 10, 1925 1,626,685 Marden et al May 3, 1927 1,668,711 Evans May 8, 1928 1,710,755 West Apr. 30, 1929 1,760,155 MacDonald et al. May 27, 1930 1,776,151 Hall Sept. 16, 1930 1,878,458 Blanchet Sept. 20, 1932 1,880,937 Elsey Oct. 4, 1932 2,095,105 Smith Oct. 5, 1937 2,276,822 Bowman Mar. 17, 1942 2,311,118 Matthews Feb. 16, 1943 2,319,413 Leathers et al May 18, 1943 FOREIGN PATENTS Number Country Date 375,971 Great Britain June 19, 1932 

